This application claims the priority of German Patent Document 100 28 148.6, filed Jun. 7, 2000, the disclosure of which is expressly incorporated by reference herein.
The present invention relates to a process for operating a press arrangement in which a press slide and at least one workpiece transport device are electromechanically driven and are electrically supplied by means of a supply and feedback device having at least one input and at least one output.
DE 195 26 491 A1 discloses a process whereby, in the event of a power failure, all devices relevant to the movement of the workpiece transport devices are supplied with voltage from an intermediate circuit. As a result, at least the workpiece transport devices can be moved into a collision-free area in order to avoid collisions with the press slide or other components of the press arrangement.
Although the process described there is very suitable for avoiding collisions and corresponding successes can also be proven, it always requires a switching-off of the press arrangement. This approach has obvious disadvantages, such as loss of production or a possibly required new setting-up of the arrangement.
An object of the present invention is to provide a process for operating a press arrangement so that despite a possible voltage drop and even a brief complete power failure, the operation of the press arrangement can continue.
According to the invention, this object has been achieved by providing that in the event of a voltage drop at the input of the supply and feedback device, the current intensity is increased at the input of the supply and feedback device.
As a result, the power fed to the drive of the press slide remains the same. Thereby the process can be continued at a constant stroke rate. In this event, the supply and feedback device is overloaded to a certain degree, so that this process can be carried out to a certain degree of the voltage drop depending on the load capacity of the supply and feedback device.
An alternative approach for achieving this objective.
As a result of the reduction of the stroke rate of the press slide carried out there according to the invention in the event of a voltage drop at the input of the supply and feedback device, the press arrangement requires a lower power, whereby the current intensity is kept constant. As a result, voltage drop compensation takes place.
What the two above solutions above according to the invention, it is advantageously achieved that, in the event of a voltage drop to the complete failure of the voltage for a certain time, the operation of the press arrangement can be continued while the normal safety measures are maintained without having to stop production completely. A restarting of the press arrangement can thus, be prevented in each case according to the invention.
When the current intensity is increased at the input of the supply and feedback device, in an advantageous further development of the process according to the invention, if the maximal current intensity of the supply and feedback device is reached, the stroke rate of the press slide can also be reduced, whereby a flowing transition between or a combination of the two above-mentioned processes is obtained.